Sensitized photographic silver halide emulsions



Feb. 23, 1937. H. A. PIGGOTT ETHAL 2, 98

SENSITIZED PHOTOGRAPHIC SILVER HAT-TIDE EMULSIONS Origin a1 Filed May '28, 19:1

SENSITIVITY RANGE OF PHOTOGRAPHIC EMULSION TREATED WITH DYESTUFF 0F EXAMPLE 1..

SENSITIVITY RANGE OF PHOTOGRAPH IG EMULSION TREATED WITH DYESTUFF 0F EXAMPLE 2.

SENSITIVITY RANGE OF PHOTOGRAPHIG EMULSION TREATED WITH DYESTUFF 0F EXAMPLE 4-.

. INVENTOR5 Henry Alfred Pi ggofl Ernesl Hurry Rudd I,

I ATTORNEY' Patented res. 232.1937 7 SENSITIZED PHOTOGRAPHIC SILVER HALIDE EMULSIONS Henry Alfred Piggott, Cheadle Hulme, and Ernest Harry Rodd, Brooklands, England, assignors to. Imperial Chemical Industries Limited, a corporation of Great Britain -Application May 28, 1931, Serial No. 540,810

Renewed June-2d, 1936.

9 Claim.

This invention relates to photographic sensitizing compositions and to photographic preparations, such as emulsions or plates or films coated with emulsions, comprising such compositions.

It is known that a standard photographic emulsion is sensitive to light rays onlywithinthewavelength range of about 360 to 500 miliimicrons, and that by suitable treatment, e. g. by bathing a photographic plate in a dilute solution of a sensitizes, the emulsion becomes sensitive to light of other wave lengths, but it is still a matter of dimculty to increase or decrease the sensitivity at will in any desired degree.

It is an object of the present invention to provide sensitizing compositions which will render photographic emulsions sensitive to light rays in the red and infra-med region of the spectrum. It is a furthercbject of this invention to provide photographic emulsions sensitive to red and infra-red light rays. It is also an objectoi this invention to provide plates and films coated with such sensitized emulsions.

'Ihese objects are achieved according to this invention by the employment of unsymmetrical polymethine dyestufis such as can be obtained by condensing a'heterocyciic nitrogen compound containing anexternal reactive methylene group with an intermediate compound obtainable by theprccess described in our English Patent No 344,409.

The accompanying drawing illustrates the sensitivity curves of photographic emulsions treated with certain of the unsymmetrical dyestufl's hereinafter described.

Examples of such uhsymmetricai dyestufi's are,

for instance, the following:

(1) Dyestuff of the formula:

'CHz OH:

osnf c-on=cn-on This dyes tii can be obtained by condensing together in" acetic anhydride solution 7 parts by weight of l:3:3-trimethyl-2-methylene-indoline and 16 parts by-weight of the product obtained according to Example 2 of English Patent No. 344,409, from quinaldine ethiodide and di- In Great Britain May phenylformamidine. The amount of acetic anhydride used should be 20 parts by weight, and the solution should be boiled under -reiiur: for ten minutes, cooled somewhat, diluted with 50 parts by weight of hot water, and vigorously stirred. The dyestufi separates out and is filtered ofi and washed.

(2) Dyestufi' of the formula:

This dyestufi" may be prepared by boiling under reflux a solution in 160 parts by weight of acetic anhydride, to which parts by weight of sodium acetate have been added, of 18 parts by weight of 2:3:3-trimethylindolenine methiodide and 24 parts by Weight of the product obtained by condensing 2-methylbenzthiazole ethiodide with diphenyliormamidlne (of. Ex-- ample 5 of English Patent No. 344,409). After boiling for fifteen minutes the mixture is diluted with 150 parts by weight of hot water, and the This dyestufl may be obtained in a manner exactly similar to (2) but using the product from 2-methylbenzoxazole ethiodide and diphe nylformamidine.

(4) Dyestufi oi the formula C2415 I a s This dyestuif is analogously obtainable from 2-methylbenzoxazole ethiodide and the product from 2-methylbenzthiazole ethiodide and diphenylformamidine, that is, by boiling under rethe benzine flux in 160 parts of acetic anhydride, to which 5 parts by weight of sodium acetate have been added, 17.92 parts by weight of 2-methylbenzoxazole ethiodide and 26.92- parts by weight of the product from 2-methylbenzylthiazole ethiodide and diphenyliormamidine. After boiling for 15 minutes the mixture is diluted with 150 parts by weight of hot water, and the precipitated dyestuii is purified by lixiviation with ether.

Other unsymmetrical dyestuifs of the polymethine series, all obtainable in a similar manner, but containing various heterocyclic nitrogen residues, may also be used according to our invention. Such dyestuffs may be represented by the general formula ACH=CHCH=B where A is a monovalent heterocyclic nitrogen residue of the type in which Ar is an o-arylene group, R is'alkyl, Y is an acid residue (such as halogen, sulphate, oxalate, etc.) and X stands for the bivalent atom or group -0-, -S, or -CR'2- (R' being allwl) and B is a divalent heterocyclic nitrogen residue of the type being alkyl) and is different from X.

The unsymmetrical polymethine dvestuiis employed in photographic emulsions in accordance with our invention may be described generically by the following formula:

x z .u \C-CH=CHCH=C Ar' l R Y a in which X represents a member of the oxygen group of elements or dialkyl methylene, Z represents a member of the oxygen group of elements, dialkyl methylene or vinylene and is different from X, Ar and Ar represent aryl radicals of series, R and R represent alkyl radicals, and Y represents the negative radical of an acid.

In carrying our invention into practical effect we treat a photographic emulsion with unsymmetrical polymethine dyestuffs as described above, e. g. by bathing a photographic plate in a dilute aqueous solution of the dyestufi. Preferably a solution of 1 part of dyestufl in 2000 parts of 50% aqueous alcohol is prepared. This stock solution is diluted for use with about-20 parts of water. c. c. of the diluted solution are taken ior each full-size photographic plate to be treated, and the plate is immersed in the solution, which is agitated gently, and kept in contact with the plate for a period of about 5 minutes. The plate is then washed with Water and dried.

whilst Z stands for --O-,

Photographic plates thus treated in accordance with our invention become sensitive as shown in the following table:-

. Plate becomes sensitive to Dyestufl (see formulae above) applied to plate wave-length range (in miliirnicrous) CH; CH:

360-653 0034 CCH=CH-CH I N\ I g I CsHS Cg: CH:

I 0.3 CCH=CH-CH=C C H| 360-600 C 435 5 I ClH-i C-CH=GHCH=O CaHl 360-640 It will be understood that these unsymmetrical polymethine dyes may be used in sensitizing any of the usual types of gelatino-silver halide photographic emulsions. These examples are purely illustrative and in no sense intended to limit the scope of the invention.

We claim:

1. Photographic gelatino-silver halide emulsions made sensitive to light of long wave-length by the application of an unsymmetrical polymethine dyestuii having the formula 2. Photographic elements coated with a gelat-. I

inc-silver halide emulsion made sensitive to light of long wave-length by the application of an unsymmetrical polymethine dyestufl? having the formula 3. Gelatino-silver halide photographic emuI- sions containing an unsymmetrical polymethine dyestufl of the general formula:

sions containing an unsymmetrical polymethine dyestufi of the general formula:

wherein X represents a member 01 the group consisting of 0, S, and dialkyl methylene; Z represents a memberof the group consisting of O, S, and dialkyl methylene and is differentfrom X, Ar and Ar represent aryl radicals of the henzeneseries, R. and R represent alkyl radicals, and Y represents the negative radical of an acid.

5. Photographic elements coated with a gelatino-silver halide emulsion containing an unsymmetrical polymethine dyestuil of the general formula:

wherein x represents a member of the group consisting of the oxygen group of elements and dialkyl methylene, Z represents a member of the group consisting of the oxygen group of elements, dialkyl methylene and vinylene and is different from X, Ar and Ar represent aryl radicals oi the benzene series, B and R represent alkyl radicals, and Y represents the negative radical of a acid.

6. Photographic elements coated with a gelatino-sllver halide emulsion containing an unsymmetrical polymethine dyestuflf oi the general formula:

wherein 'X represents a member of the group consisting of 0, S, and dialkyl methylene, Z represents a member of the group consisting of 0, S, and dialkyl methylene and is different from X, Ar and Ar represent aryl radicals of the benzine series, R and R represent alkyl radicals, and Y represents the negative radical of an acid.

7. Photographic gelatino-silver halide emulsions containing a dyestuif having thefollowing general formula:

CH; CH:

s 05 ccn=cn-cn= 'c ctm VCIa I I {Balls 8. Photographic gelatino-silver halide emulsions containing a dyestufl. having the following general formula: V

C\Hr CH1! I cg. C-CH=OHCH=C can N\ 3 3: I lHl 9. Gelatino-silver halide emulsions containing an unsymmetrical polymethine dyestuii of the wherein X and Z represent dissimilar members or the oxygen group of elements, Ar and Ar repre sent aryl radicals of the benzene series, R and R represent alkyl radicals, and Y represents the negative radical of an acid.

HENRY ALFRED PIGGOTT. mNEST HARRY RODD. 

